3o6 



WHEELER. 



[Vol. X. 



counted 24 chromatic discs, and believe this to be very close 

 to the typical number for M. glabrum. There are about three 

 times as many in the spermatozoon of M. cirriferum, Leuck. 

 I could detect no " Mittelstiick " between the head and the in- 

 sertion of the long, delicate tail. The latter has not been figured 

 or described by preceding writers. 



The spermatozoon always enters the Q.g^ at its lower, non- 

 vacuolated pole (Fig. i). What becomes of the tail during this 

 process I cannot state. Somewhat later a pair of centrosomes 

 may be observed to one side of, and obviously belonging to. 



the germinal vesicle (Fig. 2). They move apart, and the archo- 

 plasm surrounding them acquires longer and more distinct 

 radiations, which finally push in the wall of the germinal vesicle 

 in the manner shown in Fig. 3. The wall finally fades away, 

 the achromatic fibrils attach themselves to the chromosomes, 

 the huge nucleolus is left out in the cytoplasm, and the spindle, 

 which may now be recognized as that of the first polar body, 

 moves towards the apical pole, accompanied by a mass of non- 

 vacuolated protoplasm. This mass is continuous with the mass 

 at the lower pole, and constitutes with it from this time forth 

 an uninterrupted pillar running through the long axis of the 

 egg from pole to pole. The head of the spermatozoon shortens 

 and thickens, and the chromatic discs appear as deeply staining 



